This proposal seeks to develop a new bead-based array technology for simultaneously measuring catalytic activity of proteases in small volumes of cells or biological fluids. Technology of this kind is needed to accelerate research in proteomics-based diagnostics and drug discovery by enabling molecular phenotyping across large populations, and the large-scale, massively parallel screening for drug leads, which modulate protease activity. Methods will be developed that allow multiplexed protease assays to be carried out on populations on beads, with each bead-type of the population being specific to a particular protease. Basic and diagnostic applications of this technology will enable careful examination of the molecular basis of cardiovascular disease, cancer, infectious disease, and certain genetic disorders, as well as the screening for and identification of protease inhibitors, which may interfere with pathogenic aberrations of such proteases. An advantage of such multiplexed enzyme assay format is the ability to screen for inhibitors, as well as specificity of inhibition in the same screen.